But I returned that book...

No less that two or three times a day the following conversation takes place.
Me: It looks like you have a book that hasn't been returned to the library and you have a large fine on the books because it has been marked as lost.
Patron: What? I returned that book!
Me: Ok, let me do a shelf check to see if I can locate the book.
(a few minutes later) I can't seem to locate that book on the shelf, perhaps you still have it at home.
Patron: No, I am 110% sure that I returned that book. I remember it specifically because it was a rainy day and I had to get out and put the book in the book drop and I was wet and late for my gym class.
Me: Sometimes we do make mistakes but generally if we do then the book would be on the shelf. And if someone check it out then it would have been cleared from your record at that time. We have a way to mark the book that you have told us you returned it but we can find it. The system gives us 90 days to locate the book. If it is not located in that time then it will go back on your record. I encourage you to look for it in all the places that books seem to hide, behind the sofa, under the car seat, etc.
Patron: Oh, I don't need to look for it because I returned in the bookdrop. That is the last time I ever return anything in the bookdrop.
Me: Ok, you will be able to check out today, just check with us periodically to see if the book has been located. Thank you for choosing this library.

Yes, we do make mistakes but only about a quarter as many mistakes as patrons think we make. No one seems to understand, that we have heard this same story a gazillion times. There is even a Seinfeld episode about Jerry being certain he returned a book 20 years ago while in high school. The library police are out to make him pay.

True story, I looked at my account and found a DVD that I HAD RETURNED!!! was still on my account. I looked on the shelf and it wasn't there--what the hell--I returned that DVD! I remembered bringing about 5 of them bakc. Where did it go? I searched at home and it wasn't there. Then about 3 weeks later, I was cleaning my car out and found the DVD case between the gas pedal and side of the consol. I had returned 4 DVDs that day but the 5th on had slid down and hid itself.

As often as people claim that they returned their stuff in the bookdrop but never got checked in, you would think that the same people that make sock eating dryers also make the book eating bookdrops.

True story. I had one guy throw his card at me and tell me that that he was never going to use the library again and stocked out of the library. I put his card in my desk certain that I would see him again. And sure enough he sheepishly came in the next week carrying the disputed videos, telling me that they were behind where the cat always sleeps on the TV so he didn't see them.

V V has a theory, that certainanty that someone has returned item(s) to the library is inversely related to the likelihood that they didn't. If some states that they are more than 100% sure that they returned something we know that they probably didn't. On the otherhand if someone says, "Gee, I thought I returned that but wow, it could have fallen down someplace." we know that the mistake very well could be on our part.

Libraries deal with thousands of items each day. People work in libraries and people make mistakes. We work with scanners and computers that sometimes function better than other times. Mistakes are made. We admit it-so why can't you? Even a one percent error rate means that at least 10 things get jacked up each day-but in reality most days the error rate is much lower than that.